fix

vlib/v/checker/for.v

@@ -254,6 +254,9 @@ fn (mut c Checker) for_in_stmt(mut node ast.ForInStmt) {
 			}
 			if node.val_is_mut {
 				value_type = value_type.ref()
+				if value_type.has_flag(.option) {
+					value_type = value_type.set_flag(.option_mut_param_t)
+				}
 				match mut node.cond {
 					ast.Ident {
 						if mut node.cond.obj is ast.Var {

vlib/v/gen/c/assign.v

@@ -866,9 +866,19 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 							g.write('*')
 						}
 						if node_.op == .assign && var_type.has_flag(.option_mut_param_t) {
+							if val is ast.CastExpr {
+								g.expr(left)
+								g.write('->state = ')
+								g.expr(val)
+								g.writeln('.state;')
+							}
 							g.write('memcpy(&')
 							g.expr(left)
-							g.write('->data, *(${g.styp(val_type)}**)&')
+							if val is ast.CastExpr {
+								g.write('->data, ')
+							} else {
+								g.write('->data, *(${g.styp(val_type)}**)&')
+							}
 						} else if var_type.has_flag(.option_mut_param_t) {
 							g.expr(left)
 							g.write(' = ')

vlib/v/gen/c/for.v

@@ -322,7 +322,7 @@ fn (mut g Gen) for_in_stmt(node_ ast.ForInStmt) {
 				g.writeln('\t${styp} ${c_name(node.val_var)};')
 				g.writeln('\tmemcpy(*(${styp}*)${c_name(node.val_var)}, (byte*)${cond_var}[${idx}], sizeof(${styp}));')
 			} else {
-				styp := g.styp(node.val_type)
+				mut styp := g.styp(node.val_type)
 				g.write('\t${styp} ${c_name(node.val_var)}')
 			}
 			if !is_fixed_array {

vlib/v/gen/c/str.v

@@ -120,7 +120,7 @@ fn (mut g Gen) gen_expr_to_string(expr ast.Expr, etype ast.Type) {
 		exp_typ := if unwrap_option { typ.clear_flag(.option) } else { typ }
 		is_dump_expr := expr is ast.DumpExpr
 		is_var_mut := expr.is_auto_deref_var()
-		str_fn_name := g.get_str_fn(exp_typ)
+		mut str_fn_name := g.get_str_fn(exp_typ)
 		temp_var_needed := expr is ast.CallExpr
 			&& (expr.return_type.is_ptr() || g.table.sym(expr.return_type).is_c_struct())
 		mut tmp_var := ''
@@ -171,7 +171,7 @@ fn (mut g Gen) gen_expr_to_string(expr ast.Expr, etype ast.Type) {
 			}
 		} else if is_ptr && typ.has_flag(.option) {
 			if typ.has_flag(.option_mut_param_t) {
-				g.write('*')
+				g.write('/**/*')
 			} else {
 				g.write('*(${g.styp(typ)}*)&')
 			}

vlib/v/gen/c/str_intp.v

@@ -50,7 +50,7 @@ fn (mut g Gen) str_format(node ast.StringInterLiteral, i int, fmts []u8) (u64, s
 	mut base := 0 // numeric base
 	mut upper_case := false // set uppercase for the result string
 	mut typ := g.unwrap_generic(node.expr_types[i])
-	if node.exprs[i].is_auto_deref_var() {
+	if node.exprs[i].is_auto_deref_var() && !typ.has_flag(.option_mut_param_t) {
 		typ = typ.deref()
 	}
 	typ = g.table.final_type(typ)

vlib/v/markused/walker.v

@@ -1300,6 +1300,10 @@ fn (mut w Walker) mark_resource_dependencies() {
 		w.fn_by_name(builderptr_idx + '.write_string')
 		w.fn_by_name('strings.new_builder')
 		w.uses_free[ast.string_type] = true
+
+		if w.table.dumps.keys().any(ast.Type(u32(it)).clear_flags(.shared_f).has_flag(.option)) {
+			w.fn_by_name('str_intp')
+		}
 	}
 	if w.features.auto_str_ptr {
 		w.fn_by_name('isnil')